Abstract: An alkaline water electrolysis system (70) includes a rectifier (74) that is connected to a fluctuating power source and converts an AC power to a DC power; a plurality of bipolar electrolyzers (50_1) to (50_N) that generate hydrogen and oxygen through electrolysis of water using an electrolytic solution based on a predetermined DC voltage supplied from the rectifier 74; gas-liquid separation tanks (72) that are connected to the plurality of bipolar electrolyzers (50_1) to (50_N), and separate the hydrogen and the oxygen from the electrolytic solution and store the electrolytic solution; and open/close valves (62) provided between the gas-liquid separation tanks (72) and the bipolar electrolyzers (50).

Abstract: The present disclosure aims at providing an electrolysis apparatus that can efficiently produce hydrogen and can accommodate fluctuating power supplies. A bipolar zero-gap electrolyzer for water electrolysis includes multiple bipolar elements, each of which includes an anode chamber, a cathode chamber, a conductive partition wall provided between the anode and cathode chambers, and outer frames framing the conductive partition wall. The conductive partition wall has protrusions on at least one surface. A conductive elastic body is disposed between a surface of the conductive partition wall opposite the one surface and one of the electrodes. One and the other of the electrodes form conduction with the conductive partition wall at least through the protrusions and at least through the conductive elastic body, respectively. The membrane is sandwiched between the cathode and the anode of the adjacent bipolar elements by elastic stress of the conductive elastic body.

Abstract: An object of the present disclosure is to suppress mixing of gases generated during an operation when supply of electric power is stopped, to thereby shorten the time required for restarting after the electric power is stopped. An electrolysis system of the present disclosure includes an electrolyzer including an electrolytic cell in which an anode and a cathode are overlapped with each other having a diaphragm interposed therebetween, and a liquid surface level control unit which is operated when an electric conduction to the electrolyzer is stopped to adjust a liquid surface level of an electrolytic solution in the electrolytic cell.

Abstract: An electrolysis system of the present disclosure includes an electrolyzer which includes an electrode to generate a gas from the electrode, and a tightening device which controls a tightening load on the electrolyzer in accordance with a pressure of the gas.

Abstract: A method of producing hydrogen using a water electrolysis system comprising at least an electrolyzer and a purifier for removing oxygen in a hydrogen gas generated in the electrolyzer. The method includes controlling a concentration of oxygen in a hydrogen gas to be introduced to the purifier to be constantly less than 0.5 volume % when the electrolyzer is operated at least under a current density of 0.5 kA/m2 or greater; and further controlling Ob/Oa to be less than 10.0, where Oa represents the concentration of oxygen in the hydrogen gas to be introduced to the purifier when the electrolyzer is operated under a current density of 2.0 kA/m2, and Ob represents the concentration of oxygen in the hydrogen gas to be introduced to the purifier when the electrolyzer is operated under a current density of 0.2 kA/m2.

Abstract: Provided is a method of operating an electrolysis apparatus that can inhibit electrode degradation under a variable power supply. The method of operating an electrolysis apparatus includes: an energization step in which electrolysis of electrolyte is performed in an anode compartment including an anode and a cathode compartment including a cathode that are partitioned from each other by a membrane; a suspension step in which electrolysis of electrolyte in the anode compartment and the cathode compartment is suspended; and a discharge step of, in the suspension step, electrically connecting an electrolyzer of the electrolysis apparatus to an external load and adjusting a cell voltage to 0.1 V or less in 5 hours or less.

Abstract: An alkaline water electrolyzer includes at least two outer frames, a gasket, and a diaphragm. The at least two outer frames are stacked so as to overlap at least in part in a circumferential direction. The gasket is sandwiched between the two outer frames. The gasket can be in contact with the outer frames over the entire circumferential direction. In an inner peripheral surface of the gasket, a slit is formed along the circumferential direction. The gasket has a first protrusion portion. The first protrusion portion protrudes over the entire circumferential direction at a position overlapping the slit when viewed from a thickness direction of the slit. A diaphragm is caught in the slit of the gasket. A volume ratio of volume of the first protrusion portion, to volume between a bottom of the slit and an end of the diaphragm, is between 0.5 and 100 inclusive.

Abstract: A method of producing hydrogen using a water electrolysis system comprising at least an electrolyzer and a purifier for removing oxygen in a hydrogen gas generated in the electrolyzer. The method includes controlling a concentration of oxygen in a hydrogen gas to be introduced to the purifier to be constantly less than 0.5 volume % when the electrolyzer is operated at least under a current density of 0.5 kA/m2 or greater; and further controlling Ob/Oa to be less than 10.0, where Oa represents the concentration of oxygen in the hydrogen gas to be introduced to the purifier when the electrolyzer is operated under a current density of 2.0 kA/m2, and Ob represents the concentration of oxygen in the hydrogen gas to be introduced to the purifier when the electrolyzer is operated under a current density of 0.2 kA/m2.

Abstract: Provided are a gasket and an electrolyzer capable of preventing an electrolyte or a gas from leaking from a diaphragm. An annular gasket includes first and second surfaces which respectively contact a frame near a positive electrode and a frame near a negative electrode and a slit portion which is opened inward and is provided in the entire periphery of the gasket so as to accommodate an edge of an ion-permeable diaphragm.

Abstract: A bipolar alkaline water electrolysis unit incorporated in an electrolytic cell for electrolyzing an electrolytic solution of alkaline water to obtain oxygen and hydrogen, the bipolar alkaline water electrolysis unit including an oxygen generating anode, a hydrogen generating cathode, a conductive partition wall that separates the anode and the cathode from each other, and an outer frame that surrounds the conductive partition wall, wherein a gas and electrolytic solution passage is provided at an upper portion of the conductive partition wall and/or the outer frame, and an electrolytic solution passage is provided at a lower part of the conductive partition wall and/or the outer frame.

Abstract: Provided are a gasket and an electrolyser capable of preventing an electrolyte or a gas from leaking from a diaphragm. An annular gasket includes first and second surfaces and which respectively contact a frame near a positive electrode and a frame near a negative electrode and a slit portion which is opened inward and is provided in the entire periphery of the gasket so as to accommodate an edge of an ion-permeable diaphragm.

Abstract: A bipolar alkaline water electrolysis unit incorporated in an electrolytic cell for electrolyzing an electrolytic solution of alkaline water to obtain oxygen and hydrogen, the bipolar alkaline water electrolysis unit including an oxygen generating anode, a hydrogen generating cathode, a conductive partition wall that separates the anode and the cathode from each other, and an outer frame that surrounds the conductive partition wall, wherein a gas and electrolytic solution passage is provided at an upper portion of the conductive partition wall and/or the outer frame, and an electrolytic solution passage is provided at a lower part of the conductive partition wall and/or the outer frame.